RTE sources confirmed that Health Minister Leo Varadkar was lined up to do tonight's landmark television debate closing the government campaign.

But the Government insisted that the slot had to go to Communications Minister, Alex White, who is Labour's campaign director. The change was seen as a sign of continuing coalition tensions as the general election draws nearer.

However, Mr White insisted that he was always supposed to do the debate on 'Prime Time'. He said RTE talked about three slots: one for Justice Minister Frances Fitzgerald; one for Fine Gael campaign director Simon Coveney; and the last one for himself on Labour's behalf. "There is absolutely no problem between myself and Leo," the Communications Minister said.

The two largest opposition parties in the Dáil have meanwhile criticised RTE for only including Government parties in their television and radio coverage of the marriage equality referendum.

Fianna Fáil sent a letter of complaint to RTE Director General, Noel Curran, on Saturday and have yet to receive a response, while Sinn Féin wrote to Mr Curran yesterday and are expected to follow that up with a phone call today.

RTE responded to the Irish Independent on the letter from Fianna Fáil, but denied receiving a complaint from Sinn Féin at the time, despite the party confirming a letter had been sent on Monday.

“RTE has taken care to balance the debates with a range of voices across the political spectrum and beyond. Referendum debate panels are not selected on party political lines,” said a spokesperson.

“I am aware of the press release that Sinn Fein issued but we have received no letter from Sinn Fein today that we can confirm.”